Hole straightening device



Oct. 27, 1964 T. F. MOORE ETAL 3,154,156

HOLE STRAIGHTENING DEVICE Filed Dec. 16, 1960 3 Sheets-Sheet 1 1INVENTORS ATTEST Thomas F. Moore,

- L James M. Cleory mg, W

Attorney Oct. 27, 1964 T. F. MOORE ETAL 3,154,156

, HOLE STRAIGHTENING DEVICE Filed Dec. 16, 1960 3 Sheets-Sheet v2 Fig. 4

INVENTORS ATTEST Thomas F. M0 Q2 2 James M.C y a "W 24:04

Attorne'y Oct. 27, 1964 T. F. MOORE ETAL 3,154,156

HOLE STRAIGHTENING DEVICE Filed Dec. 16, 1960 3 Sheets-Sheet 3 7 a ll 23INVENTORS II A Thomas F. Moore, F g. 5 James M. Cleury ATTEST M 54;, oz}Aflorney United States Patent 0 3,154,156 HOLE STRAIGHTENING DEVICEThomas E. Moore and James M. Oleary, Dallas, Tea,

assignors to The Atlantic Refining Company, Philadelphia, Pa, acorporation of Pennsylvania Filed Dec. 16, 1%(3, Ser. No. 76,365 6Claims. (Cl. 17576) This invention pertains to a means and method ofrotary drilling that produces a borehole approaching gravitationalvertical. More specifically, the present invention relates to anelongated, automatically self-orienting, rotatable sleeve which urges adrilling means to follow a gravitational vertical path.

It is well known that earth drilling bits tend to drift thereby drillingcrooked holes. This drifting creates many problems in earth drilling,among which are drill-stem fatigue, pinching and freezing of the bit,increased collar wear and key slotting, decreased drilling rates,non-uniform drill bit wear and dry holes.

Prior attempts to alleviate these problems of crooked holes have beenmany and varied, but, in general, unsatlisfactory. One group of deviceswere developed to straighten boreholes already deviated from vertical.These latter devices are usually called directional drilling devices andconsist of means for controlled deflection of a bit. Normally, thesedirectional devices are manually oriented to force the bit in one setcompass direction. Once these devices are put in operation, thedirection of deflection cannot be altered without deactivating,reorienting and reactiviating the device. This seriously limits theiruse in routine drilling of vertical boreholes and they are, in general,uneconomical and unsuitable for this purpose.

Other attempts at eliminating crooked holes have been concernedprimarily with means for stabilizing the bit and drilling straightboreholes instead of vertical boreholes. These stabilizers tend toresist any deflection of the drill bit. But they do not prevent agradual change in direction; therefore, if the bit gradually drifts fromvertical but maintains a substantially straight borehole, thesestabilizers will not cause the bit to return to vertical. Where thesestabilizers were described as drilling vertical boreholes, the devicesrelied on the plumb-bob or pendulum effect. This effect exists when thedeviation from vertical exceeds an angle at which the pull of gravity onthe bit and drill collars prevents the forces tending 'to deflect thebit from causing added deviation. Occasionally, however, the causes ofthese deflecting forces abruptly change and the pull of gravity causestoo rapid a change in direction. The plumb-bob effect, therefore, is nota reliable cure for crooked holes.

Other devices allegedly designed to drill vertical boreholes actuallyincrease non-uniform bit wear, drill collar wear, bending stresses andkey slotting in the vicinity of the bit because they tend to cock orwobble the bit and drill collars.

Presently available equipment, therefore, is either ineffective fordrilling a vertical borehole or has undesirable characteristics. It isan object of this invention to provide an economical and practicaldevice and method for drilling vertical boreholes without increasingdrill collar wear, bending stresses and non-uniform bit wear.

It is a further object of this invention to provide an automatically,self-orienting, lateral force applying means to deflect the drill bitback to vertical even if the borehole is straight.

Another object is to provide a means which may perform as a controlledunstabilizer urging the drill bit to follow a substantially verticalpath.

Yet another object is to provide means for automatically orienting alateral force in relation to the earths center of gravity.

a vertical to an exaggerated degree.

3,154,155 Eatented Oct. 27, 1964 A further object is to provide arelatively simple device which can be readily utilized in conjunctionwith devices controlling the rate of deviation of a borehole.

Still another object is to provide a borehole straightener whoseprinciples of operation can be adapted to many forms and whose operationcan be made intermittent.

Further advantages and objects will become apparent after reading thisspecification and examining the accompanying drawings showing simplifiedembodiments of this invention.

In the drawings,

FIGURE 1 is a fragmented, elevational view of a borehole straighteningdevice in the position that it will assume when the borehole deviatesfrom vertical.

FIGURES 2 and 3 are transverse, cross-sectional views taken as indicatedby 2-2 and 33 on FIGURE 1. FIGURE 2 shows a stop means which orients aforce means whose position relative to the stop means is shown in FIGURE3.

FIGURE 4 is a fragmented, elevational, cross-sectional view showing theinternal construction of the borehole straightening device of FIGURE 1.

FIGURE 5 is a fragmented, elevational, partial, crosssectional viewshowing an alternative means for applying a straightening force to thedevice of FIGURES 1 and 4.

FIGURE 6 is a fragmented, elevational, cross-sectional view showing analternative means for orienting the force means of the device shown inFIGURES l and 4.

In rotary earth drilling, when the borehole deviates from vertical, thedrill collars immediately above the bit will buckle to the low side ofthe borehole. The distance from the bit to the point of tangency of thisbuckle and borehole wall varies with the degree of borehole deviationand shifts downward toward the bit as the degree of deviation increases.This invention utilizes this buckling phenomenon to control a lateralforce which urges the bit to return to a vertical path. Generally, thisinvention comprises an elongated, frictionally mounted, rotatable sleeveof sutficient length to be measurably influenced by the lowest naturallyoccurring buckle in the drill collar string. The sleeve is mounted onthe drill collars immediately above the bit. Near the lower end of thesleeve in the vicinity of the bit is a lateral force applying meanswhose direction of application is controlled by the sleeve. On thesleeve above the force means is a stop means which in relation to thedirection of rotation leads the force means by circumferential spacingof not more than 180. The stop means and force means arecircumferentially oriented in relation to each other so that the forcemeans is directed to the high side of the borehole whenever the stopmeans prevents rotation of the sleeve. Briefly, in operation, the sleeveis normally rotated by rotation of the drill collars and advancement ofthe drill hit. As the borehole deviates from vertical, the collarsbuckle to the low side of the borehole deflecting the sleeve in the samedirection and causing the stop means to contact the wall of the boreholethereby preventing further rotation of the sleeve. This orients theforce means toward the high side of the borehole so that its lateralforce urges the bit toward vertical.

For more detail, referring now to the drawings and in particular toFIGURE 1, there is indicated a borehole which for illustrative purposeshas been deviated from Drill collars 11 are shown as adapted to thisinvention. Removably attached to the lower end of these drill collars isconventional drilling means 13 that represents any form of drillingmeans that can be rotated by a drill string. Frictionally and rotatablymounted about a portion of drill collars 11 is elongated sleeve 15 ofsufiicient length to utilize the influence of the first naturallyoccurring buckle in drill collars 11 above drilling means 13. The lengthof sleeve 15 is, therefore, dependent on the flexibility of the drillcollars, the Weight of and on the drill collars and the degree ofborehole deviation. Since, in normal drilling operations, drill collars11 are substantially inflexible, the length of sleeve 15 will exceedtwenty-five feet and usually be nearer fifty feet. Because of thislength, the sleeve will frequently extend over several drill collars andmay be formed of several sections threaded together.

Normally, sleeve 15 tends to rotate with drill collars 11 because of thefriction between sleeve 15 and drill collars 11. 7

As shown in FIGURE 1, near the upper end of sleeve 15 is stop 17 whichstrikes the wall of the borehole when the upper end of sleeve 15 isbuckled toward the low side of the borehole by drill collars 11. In thisposition,

.stop 17 prevents further rotation of sleeve 15 thereby holding itstationary while drill collars 11 are freely rotated therein. FIGURES 1and 2 show stop 17 as a rigidly mounted, single, protruding,longitudinal rib whose leading face surface 19 is a flat, smooth,surface and whose upper end in relation to the direction of rotationcircumferentially leads the lower end thereby inclining leading facesurface 19. This inclination in the leading face surface acts to preventstop 17 from digging into and wedging into the formation because asdrilling means 13 is advanced into the borehole, inclined leading facesurface 19 presses against the formation and tends to rotate the stop ina direction opposite to the direction in which the drilling means isrotated. The trailing surface of stop .17 is shown in FIGURE 2 asrounded and gradually tapering to the surface of sleeve 15. It should benoted that stop 17 can be in any form that does not prevent rotation ofthe drill collars inside the sleeve. For example, stop 17 could bespring biased instead of rigidly mounted, and could be retractable tofacilitate fishing or jarring operations if the drilling means or sleeveshould become wedged or pinched in the borehole. Moreover, the stopcould be made of frangible materials or hardened rubber for similarreasons. In addition, the stop could be utilized in drilling operationswhere the drilling means is rotated both clockwise and counterclockwiseas viewed from the surface. In such cases, the stop could be movablyfitted to the sleeve so that changing the direction of rotation wouldslide the stop to a new position dependent on the design of thatparticular sleeve and the stop would have faces similar to leading facesurface 19 in both directions. The stop could also be designed to openand close valve ports to control the application of a hydraulicallyoperated force means as described later.

The distance that stop 17 protrudes from sleeve 15 is determined by therelative diameters of the sleeve and borehole and by the length of thesleeve and the factors controlling this length as mentioned previously.

Near the lower end of sleeve 15 is lateral force applying means 21 whichin FIGURE 1 is shown as a bow spring exerting a substantiallycontinuous, predetermined, lateral force on drill collars 11 anddrilling means 13. As shown, force means 21 is circumferentially spaced90 from stop 17 and trails the stop in the direction of rotation.It'should, however, be recognized that the circumferential spacing offorce means 21 and stop 17 may be varied from 90 so long as force means21 trails stop 17 with relation to the direction of rotation of drillcollars 11 and the circumferential spacing is not more than 180. Asshown by FIGURES 1, 2 and 3, force applying means 21 is oriented inrelation to stop 17 so that its force is applied against the high sideof the borehole when stop 17 prevents rotation of the sleeve. Forcemeans 21 thereby deflects drilling means 13 away from the high side ofthe borehole or, in other words, toward gravitational,

vertical.

Force applying means 21 can be any suitable device for applying alateral force to the bit, e.g., a mud jet, an expansible and retractablehydraulically operated plate or rod, a spring loaded rod or plate, or apermanent bow in the lower end of the sleeve. Moreover, lateral forceapplying means 21 could be made to operate intermittently orcontinuously. For example, the force means could be a hydraulicallyactivated, retractable plate Whose force would only be applied when stop17 pushes, against the wall of the borehole and opens portscommunicating with the high pressure drilling fluids used in rotarydrilling. In another example, both the stop and force plate could benormally retracted and be connected by suitable ports to the highpressure drilling fluid. The stop and force plate would be activatedonly upon closing a flow channel thereby restricting the flow ofdrilling fluid through the bit and raising the pressure in the drillingfluid high enough to expand the stop and force means or the mud pumppressure could be increased to expand the stop and force means.Moreover, the sleeve or drilling means could incorporate devices tocontrol the rate of deviation of the drilling means to prevent forcemeans 21 from causing too rapid a change in direction.

Referring now to FIGURE 4, the mounting of sleeve 15 to drill collars 11is shown. The sleeve shown in FIGURE 4 is sealed at both ends bysealrings 23 and annulus 25 between drill collars 11 and sleeve 15 isfilled with lubricant. The lower end of sleeve 15 is mounted to thedrill collars on ball bearings 27 for rotation of the collars inside thesleeve. The rest of sleeve 15 is mounted in friction bearings 29. Thereis enough friction between sleeve 15 and drill collars 11 that sleeve 15tends to rotate with the drill collars until stop 17 prevents furtherrotation of the sleeve. Force means 21 will, therefore, tend to changedirection until stop means 17 prevents further rotation of the sleeve.

FIGURE 4 shows but one embodiment for mounting the sleeve. The sleevecould be mounted to the collars in a clamp around fashion to permit easyremoval thereof. Moreover, the sleeve could be mud lubricated bypermitting mud to flow continuously through the sleevecollar annulus 25.

The operation of the hole straightening device is best understood byreference to FIGURES 1 and 4. During drilling, drill collars 11 arecontinuously rotated as drilling means 13 advances. As drill collars 11are rotated, sleeve 15 rotates. As sleeve 15 rotates, force means 21continuously applies a lateral force to drilling means 13 tending tounstabilize the drilling means and cause it to drift, but since forcemeans 21 is continuously changing in direction the amount of drift isslight. This could cause drilling means 13 to follow a slightlyspiralling path. This continuously changing force tends to preventuneven wear of the drilling means and to decrease the natural tendencyof the drilling means to seek a gradually drifting path. When drillingmeans 13 drift from vertical 7 as shown in FIGURE 1, drill collars 11will buckle to the low side of the borehole and in turn buckle sleeve 15toward the low side. When this occurs, stop 17-starts to impede rotationof the sleeve until the buckle is sufficient for stop 17 to pressagainst the borehole wall with sufficient force to prevent furtherrotation of sleeve 15;

Force means 21 being oriented in relation to stop 17 is then placedtoward the high side of the borehole and continuously applies its forcein one direction thereby deflecting drilling means 13 from the high sideuntil the borehole returns to a vertical path and stop 17 no longerprevents the sleeve from rotating. The sleeve, therefore, automaticallyorients a straightening force to urge the drilling means to follow asubstantially vertical path regardless of the straightness or" theborehole.

In FIGURE 5, there is shown an alternative means for applying a force todeflect the bit back to vertical. The sleeve 15 has a permanent bow inits lower portion. This permanent bow is oriented with relation to stop17 so that the bow is placed toward the high side of the borehole whenstop 17 prevents further rotation of the sleeve. In operation, as theborehole deviates from vertical, stop 17 prevents rotation of sleeve 15and places the permanent bow in sleeve 15 toward the high side of theborehole. Upon further deviation, drill collars ll tend to buckle insidesleeve 15 to conform to the permanent bow and this places the firstbuckle in the drill collars above drilling means 13 on the high side ofthe borehole causing the drilling means to be deflected toward the lowside and return to vertical.

In FIGURE 6, there is shown an alternative stop means. The sleeve 15 hasa permanent bow in its upper portion. This permanent bow is oriented at180 from force means 21 so that force means 21 is placed toward the highside of the borehole when the permanent bow prevents rotation of thesleeve. In operation, as the borehole deviates from vertical, drillcollws 11 buckle to the low side of the borehole and when the buckle issufiiciently large, the permanent bow in sleeve 15 will align with thebuckle in the drill collars and sleeve 15 will no longer rotate with thedrill collars. At this point, force means 21 is placed on the high sideof the borehole and deflects drilling means 13 back to vertical.

The above description of this invention details three simplifiedembodiments capable of performing all the objects set forth herein; butthis invention is not limited to these specific details. We reserve theright to variations or modifications that are apparant to those skilledin the art and that are within the scope of the following claims.

We claim:

1. In a borehole drilling apparatus having a drilling means rotated by adrill collar string, an improved borehole straightener comprising asubstantially inflexible, elongated, cylindrical sleeve rotatably andfrictionally mounted about said drill collar string adjacent saiddrilling means, force applying means formed on the lower end of saidsleeve, stop means located on said sleeve above said 6 force applyingmeans and leading said force applying means with relation to thedirection of rotation of said rill collar string by a predeterminedangle of not more than degrees, said stop means being adapted to engagethe wall of said borehole and prevent rotation of said sleeve with saiddrill collar string at such times as the borehole deviates from verticalby a predetermined amount, and said force applying means being adaptedto apply a lateral force to the lower end or" said sleeve to urge saiddrilling means toward vertical at such times as said stop means preventsrotation of said sleeve with rotation of said drill collar string.

2. A borehole straightener in accordance with claim 1 wherein the forceapplying means is a bow spring.

3. A borehole straightener in accordance with claim 1 wherein the forceapplying means is a permanent bow in the lower end of the sleeve.

4. A borehole straightener in accordance with claim 1 wherein the stopmeans is a single protruding rib.

5. A borehole straightener in accordance with claim 1 wherein the stopmeans is a permanent bow in the upper end or" the sleeve.

6. A borehole straightener in accordance with claim 1 wherein the lengthof the sleeve is at least twenty-five feet.

References Cited in the file of this patent UNITED STATES PATENTS2,061,316 Brack et al Nov. 17, 1936 2,316,409 Downing Apr. 13, 19432,329,597 Diehl et al Sep. 14, 1943 2,734,721 Zublin Feb. 14, 19562,745,635 Zublin May 15, 1956 2,841,366 Dunn July 1, 1958 2,915,286Wright Dec. 1, 1959

1. IN A BOREHOLE DRILLING APPARATUS HAVING A DRILLING MEANS ROTATED BY ADRILL COLLAR STRING, AN IMPROVED BOREHOLE STRAIGHTENER COMPRISING ASUBSTANTIALLY INFLEXIBLE, ELONGATED, CYLINDRICAL SLEEVE ROTATABLY ANDFRICTIONALLY MOUNTED ABOUT SAID DRILL COLLAR STRING ADJACENT SAIDDRILLING MEANS, FORCE APPLYING MEANS FORMED ON THE LOWER END OF SAIDSLEEVE, STOP MEANS LOCATED ON SAID SLEEVE ABOVE SAID FORCE APPLYINGMEANS AND LEADING SAID FORCE APPLYING MEANS WITH RELATION TO THEDIRECTION OF ROTATION OF SAID DRILL COLLAR STRING BY A PREDETERMINEDANGLE OF NOT MORE